1. Technical Field
This invention relates in general to semiconductor manufacturing and, more specifically, to in-line testing of flip-chip semiconductor assemblies.
2. State of the Art
As shown in FIG. 1, in a conventional process 10 for manufacturing flip-chip semiconductor assemblies, singulated dice are flip-chip attached with a conductive epoxy or solder to a printed circuit board (PCB) or other substrate to form a flip-chip semiconductor assembly. Once the dice are attached by curing of the epoxy or reflow of the solder, the dice are then encapsulated, underfilled, or both, using a non-conductive epoxy or other encapsulation material. The electrical characteristics of the flip-chip semiconductor assembly are then tested and, if the assembly passes the test, it is selected for shipping to customers.
If the flip-chip semiconductor assembly does not pass the test, then it proceeds to a repair station, where it is repaired using one or more known-good dice (KGD) 12 (i.e., dice that have already passed all standard electrical tests and have been through bum-in). Specifically, those dice in the assembly that are believed to have caused the assembly to fail the test are electrically disconnected from the rest of the assembly, typically using laser fuses. One or more KGD are then attached to the PCB of the assembly to replace the disconnected dice. Once the KGD are attached, the assembly is retested and, if it passes, it too is selected for shipping to customers.
The conventional KGD repair process described above generally works well to repair flip-chip semiconductor assemblies, but the process necessary to produce KGD can be an expensive one. Also, the described KGD repair process does not test for, or repair, problems with the interconnections between the dice and the PCB in a flip-chip semiconductor assembly. Rather, it only repairs problems with non-functioning dice or defective solder bumps. Finally, the KGD in the described repair process end up going through burn-in twice a first time so they can be categorized as a KGD, and a second time when the flip-chip semiconductor assembly to which they are attached goes through burn-in. This is obviously a waste of burn-in resources and also stresses the KGD far beyond that necessary to weed out infant mortalities.
Therefore, there is a need in the art for a method of testing flip-chip semiconductor assemblies that reduces or eliminates the need for the KGD repair process described above.